This invention relates to a machine for forming, filling, and sealing reclosable bags from a continuous web of bag material, and more particularly to a mechanism for guiding the bag film and separating the bag film's fastener elements in such a forming, filling, and sealing machine.
Bags of various types have been used for packaging a wide variety of products. For example, cereals, cookies, and potato chips are often packaged in bags. These bags can serve as the external packaging for the products, or can be inserted into boxes as a liner for the boxes. When packaging perishable materials such as cereal, cookies, and potato chips, the bags should be sealed, as sealed bags help to preserve the product contained therein by preventing the co-mingling of outside air and moisture with the product in the bags.
Conventional sealed bags (such as most cereal bags and potato chip bags) have seals which are formed by gluing together or heat sealing together a pair of opposed edges of the bags. One problem with such conventional sealed bags is that they cannot be resealed after being opened. Thus, once the bag is opened, the user cannot prevent the unwanted intrusion of outside air and moisture into the bag.
Reclosable bags are known. Usually, reclosable bags include a pair of fastener elements (such as a pair of rib and groove profiles or "zippers"), which the user fastens together after opening to thereby effectively seal the contents of the bag from the intrusion of unwanted air and moisture. One example of such a reclosable bag is the ZIPLOC.RTM. brand food storage bag manufactured by the Dow Chemical Company, the assignee of the instant application.
Both conventional and reclosable bags share a common feature in that they are usually formed from a continuous roll (web) of bag film. This bag film web is filled with the product (such as cereal) and the web is subdivided into a plurality of individual bags.
Machines for forming and filling bags from a continuous web of bag material are known.
Toss, U.S. Pat. No. 3,815,317 relates to a form, fill, and seal apparatus for use with zippered bags. A continuous web of bag film is fed to the apparatus. The continuous web of bag film has interlocked fasteners. The fasteners are disengaged, and the film spread apart to remove wrinkles. A pin unlocks the fasteners, while a guide device holds the fasteners apart. The fasteners are rejoined as they are pinched by closing rolls. The interlocked bag film is then cross-sealed and filled through the remaining open side. The final seam is then sealed and severed to provide the final structure. It should be noted that the mechanisms in the Toss structure which unlock and reclose the fasteners do so for the purpose of removing wrinkles or folds from the bag film. The filling of the bag itself is accomplished through an open side of the bag film. During the filling of the bag, the profiles are closed.
Boccia, U.S. Pat. Nos. 4,024,010 and 4,094,729 have a parent/divisional relationship. Boccia relates to an apparatus wherein two opposing film layers with interlocking rib and groove fasteners on opposing faces are separated so that a heat sealing of the side seams can be accomplished only in those areas where the fasteners remain interlocked. A separating finger opens the interlocked fastener elements. Grooves on the top and bottom of the separating finger are provided for maintaining the fastener elements in alignment.
One difficulty encountered in bag forming, filling and sealing operations is maintaining the bag film from which the bags are cut in a proper lateral alignment as the bag film travels through the forming, filling and sealing machine. This problem is especially acute in the forming, filling and sealing of fastener element containing recloseable bags.
Typically, reclosable bag film is wound on a roll in a helical pattern, wherein the fastener elements of adjacent layers on the roll are offset laterally from each other. Reclosable bag film is usually wound on a roll in this manner in order to form a roll having a more constant diameter throughout its width. If the bag film were not wound in this helical arrangement, the extra thickness of the fastener elements would cause the bag film roll to be much thicker in that area wherein the zippers were placed. The helical winding of the bag film roll makes it difficult to draw the web from the roll in a proper lateral alignment for entry into the forming, filling and sealing machine. As the web should be properly laterally aligned before the web is fed into the machine, means should be provided for laterally aligning the web prior to the web being fed into the forming, filling and sealing portions of the machine.
It is therefore an object of this invention to provide an improved bag film guiding and aligning means for a packaging machine.